Baseball umpires make worse decisions on polluted days. "Unique characteristics of this setting combined with high-frequency data disentangle effects of multiple pollutants and identify previously under-explored acute effects. We find a 1 ppm increase in 3 hour CO causes an 11.5% increase in the propensity of umpires to make incorrect calls and a 10 µg/m³ increase in 12-hour PM2.5 causes a 2.6% increase." Archsmith et al 2018.